On Tue, May 17, 2011 at 08:05:31PM +0000, Jk . wrote:
>> Hi,
>>> I would like to submit this patch for discussion with other developers and maintainers.
>>> It enables another RTP payload for MPEG4 Audio: Low-overhead MPEG-4 Audio Transport Multiplex (LATM). The format specification is described in RFC 3016, and the encoding specifications are provided in ISO/IEC 14496-3.
>>> I believe this is an important feature for the RTP format, because it significantly reduces the overhead of MPEG4-GENERIC streams, and as stated in the RFC "In audio-only applications, then, it is desirable for LATM-based MPEG-4 Audio bitstreams to be directly mapped onto the RTP packets without using MPEG-4 Systems".
>>> MPEG4-GENERIC allows for transport of a wide range of content, including Java applets (MPEG-J) and scripts, this is the reason of the extra overhead compared to MP4A-LATM which only transports audio. The header size of MP4A-LATM in all the tests i've made is only 1 byte. The only scenario where this header size will be bigger than 1B is when the audio frame size is larger than 254B. But, on average the audio frame is 200B.
>>> Also, with this payload, there is no need of '-flags +global_header' because all the needed SDP parameters are created on the fly from the AVCodecContext object, the user will only need to specify "-fflags +latm" to enable MP4A-LATM instead of the default MPEG4-GENERIC.
>>>> P.D. If the maintainer is OK with this patch, please commit it to the trunk.
commited and pushed with some changes from martin
thanks
> And let me know the revision number.
git-N-30060-g6efb296
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
Let us carefully observe those good qualities wherein our enemies excel us
and endeavor to excel them, by avoiding what is faulty, and imitating what
is excellent in them. -- Plutarch
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 198 bytes
Desc: Digital signature
URL: <http://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20110520/7fc092aa/attachment.asc>